Computer systems typically include components such as processors, power supplies, nonvolatile storage, peripheral devices, etc. The components require power and some way to communicate with each other. These components frequently reside on one or more printed circuit boards that provide both mechanical support and electrical connectivity as a result of electrically conductive traces on the board.
The boards are architected to maintain the signal amplitude and switching rise time for signals communicated on the electrical traces. As the frequency of communication increases, circuit board losses tend to degrade the quality of the signals.
Signal repeaters may be incorporated in the architecture to maintain the signal amplitude and rise time. Adding signal repeaters between components, however, increases cost and complexity of the printed circuit board.
Differential signaling may be used to extend the useful frequency of operation of the board. Differential signaling, however, requires dual traces with matched impedances for every signal path.
High-speed traces tend to be sources of electromagnetic interference (EMI) that may require costly shielding. Moreover, losses such as dielectric losses and skin effect increase with frequency and place an upper bound on the useful electrical operating frequency of the printed circuit board.